My 600D is with firmware 1.0.1. Unfortunately, this 1.0.1 lead to blinking LED when installing the ML. The links to Canon UK web site from the wiki site is dead now. Even more unfortunate for me, the vimeo.com which is said to have a mirror is blocked for my country for unknown reasons. And I do not know whether there is a way to update the Canon firmware to appropriate subversion.
Issue #1128 resolved